#include<iostream>
#include<cstring>
using namespace std;
typedef long long LL;
const int N = 2e5 + 10, M = N * 2;
int h[N], e[M], ne[M], idx, w[M];
int dis[N];
LL d[N];
int n, m, q;
int f[N][24];
LL sz[N];
void add(int a, int b, int c)
{
	e[idx] = b, w[idx] = c, ne[idx] = h[a], h[a] = idx++;
}

void dfs(int u, int fa)
{
	//if(u!=1)sz[u] = w[h[u]];
	//cout<<"u=="<<u<<endl;
	//cout<<"ans=="<<w[h[u]]<<endl;
	for (int i = h[u]; ~i; i = ne[i]) {
		int j = e[i];
		if (j == fa)continue;
		dis[j] = dis[u] + 1;
		f[j][0] = u;
		for (int k = 1; (1 << k) <= dis[j]; k++) {
			f[j][k] = f[f[j][k - 1]][k - 1];
		}
		sz[j] += sz[u];
		sz[j] += (LL)w[i];
		dfs(j, u);
		//sz[u] += sz[j];
	}
}

int lca(int a, int b)
{
	if (dis[a] < dis[b])swap(a, b);
	int d = dis[a] - dis[b];
	for (int i = 0; d; i++) {
		if (d & 1)a = f[a][i];
		d /= 2;
	}
	if (a == b)return a;
	for (int i = 23; i >= 0; i--) {
		if (f[a][i] != f[b][i]) {
			a = f[a][i];
			b = f[b][i];
		}
	}
	return f[a][0];
}

void dfs2(int u, int fa)
{
	for (int i = h[u]; ~i; i = ne[i]) {
		int j = e[i];
		if (j == fa)continue;
		d[j] += d[u];
		dfs2(j, u);
	}
}
int main()
{
	cin >> n >> m >> q;
	memset(h, -1, sizeof(h));
	for (int i = 0; i < n - 1; i++) {
		int a, b, c;
		cin >> a >> b >> c;
		add(a, b, c);
		add(b, a, c);
	}
	dfs(1, 0);
	//cout<<sz[2]+sz[3]-2*sz[lca(2,3)]<<endl;
	while (m--) {
		int a, b, c;
		cin >> a >> b >> c;
		d[a] += c;
		d[b] += c;
		int k = lca(a, b);
		//cout<<"k=="<<k<<endl;
		//d[k] -= (LL)2 * c;
		d[k] = d[k] - (LL)2 * c;
	}
	// 	for(int i=1;i<=n;i++){
	// 	    cout<<"i=="<<i<<endl;
	// 	    cout<<"d[i]=="<<d[i]<<endl;
	// 	}
	dfs2(1, 0);
	while (q--) {
		int a, b;
		cin >> a >> b;
		LL ans1 = (LL)d[a] + d[b] - 2 * d[lca(a, b)];
		LL ans2 = (LL)sz[a] + sz[b] - 2 * sz[lca(a, b)];
		//cout<<"ans1=="<<ans1<<endl;
		//cout<<"ans2=="<<ans2<<endl;
		cout << ans1 + ans2 << endl;
	}
	return 0;
}